Maybe because there is no "mobile web"? I mean, there's the Web. There's the mess that smartphones make of it. And there's the mess that devs make designing for smartphones. But that's not a problem with the Web.
That sure sounds like a problem, and the problem exists on the web. "Mobile web" is a useful and descriptive name for the bit of the web that suffers most from this problem.
Not at all. If I have a small computer, even a smartphone, running Linux, there is no problem. Except that its screen is too damn small, and demand for AR headsets never took off.
Leaving the title as 'Developing for mobile' makes it sound like it's referring to native mobile development. This article is definitely about web development, specifically when targeting mobile devices.
"Developing for Android and iOS browsers" would be more accurate.